However, last year British-American held a conference at which it was mentioned that the Dutch, because of their excellent language education and proficiency, should be considered as native speakers.
I can remember reading a report on the internet some time ago (can't find a link right now) that claimed the Dutch were the best non-native speakers of English in the world.
i've always thought the danes were pretty damn good.
"vast and black. the thing that was poised, like a crow over the moon. round and smooth. cannon balls. things that have fallen from the sky to this earth. our slippery brains. things like cannon balls have fallen, in storms, upon this earth. like cannon balls are things that, in storms, have fallen to this earth. showers of blood. showers of blood. showers of blood. " c.f.
I received an email from my former employer, prior to the start of my employment, that said something along the lines of, "We have one two women from Liverpool, an Australian, a South African (who is white), and may get a Cameroonian." I had sent an email asking about the current/other foreign teacher staff. The South African was an Afrikans-speaking fascist with pederast tendancies and a thick, thick accent. He was hired as a native speaker despite the fact that he was, in fact, not.
I just thought it was funny/sad/weird that the emailer thought they had to qualify S. African with "white." And if you think the Cameroonian and South African didn't get along like oil and water... yeah, you'd be about right.
As others have said, as long as you're white you shouldn't have a problem. if you go through an agency they're likely to say you're a native speaker anyway - the school won't need your passport - and nobody is ever likely to find out. As far as I'm concerned you're a native speaker anyway; the only way you're likely to be deficient is in your idiomatic range, but that would probably be mitigated at your greater mastery of grammar. You may have a 'European' accent but the only thing a Thai would be capable of discerning was that you weren't American.
At my last school, I'd been there about 8 months before a Thai assistant told me all the teachers thought I was Swedish (I'm English). Can't say it bothered me (better than thinking I was a Brummie).